The invention relates to a process and device for detecting the speed and direction of rotation of a rotary drive.
It is known in the art to detect the speed and direction of rotation of a rotary drive by means of two Hall sensors off-set by 90.degree.. To this end a N-S magnetized ring magnet is mounted centrally on the rotary drive axis and is connected rotationally secured thereto. During rotation of the ring magnet the two Hall sensors mounted at the sides of the ring magnet are each infiltrated by a variable magnetic field. The changes in the magnetic field thereby occurring at the two sensors are converted by a Schmitt trigger into two binary impulse sequences off-set by 90.degree. relative to each other. By counting the number of impulses per unit time it is possible to determine the speed and by comparing the two impulse sequences it is possible to determine the direction of rotation of the rotary drive.
The disadvantage with this process is the expensive housing structure which results from using two Hall sensors and their 90.degree. off-set arrangement. Connected with this is also the cost-intensive contacting and connection of the two Hall sensors.
From DE 40 38 284 A1 a process is known for detecting the position and direction of movement of translatory or rotary moving parts of an assembly which derives from a rotary drive of the assembly numerical impulses in rotary direction coded impulse sequences or numerical impulses with rotary direction coded form. To this end in particular a disc is provided connected to the rotary drive and having a ring with a predetermined number of marks arranged in sequence. Next to the disc in the area of the ring is a Hall sensor which responds to these marks.